Children and grandparents

Hi, I was hoping to get some advice, very tricky situation. Myself and stbxh, still live in the same house. He initiated divorce on my unreasonable behaviour, because he decided after 15 years of marriage that the grass is going to be greener and instead of discussing anything with me, well he did for five min, he woke up one morning and decided he wanted a divorce. We are in the middle of battling out the finances and he has been very dishonest about what he has.
Obviously I'm trying to keep everything as normal as possible for our child, and to keep a good relationship with his parents, however the Mother has decided to plan days out with our child and nights away from home, but has not discussed this with me. I have been told this is happening and I just have to go with it. Don't get me wrong, I really don't mind them going out, but just the common decency to discuss it with as the mother of my child! If I say any thing about it to my stbex, he either kicks off or tells me I don't have a say. I will be the primary carer for our child, he really couldn't be bothered and if he has spent anytime with our child since this started we are lucky! So the advise I am looking for really is do I say something at the risk that it will all kick off or do I just let it go? I'm perfectly happy for my child to spend time with her grandparents, but they seem to have forgotten that there is a mother to.
His parents are the reason we have not settled the financials yet, they keep sticking their oar in and telling him not to disclose everything so I get less and that he will not have to pay child care!! We both want to keep it out of court but can see it happening.

Any advice would really be appreciated. Or if anyone has been in the same situation that can offer any advice.

Hi I can only speak of my experience. His parents are divorced and from day one his father and step mum have tried to help us and have on occasion just been such a support for me. His mother on the other hand has cut me off completely. I spent my first two years driving the two hundred miles every few months so the children could keep relationships with all of their grandparents, they all live in Essex. However just before the final court hearing after a five hour journey we arrived at his mothers and I was asked to just leave the children and they would get them to the other grandparents later. I was hurt beyond belief, cut off after twenty years. To be honest I haven't been back since and she therefore hasn't seen the children for over a year now. We still have a fantastic relationship with his father and step mum as they refuse to be bullied by my ex. They were also told to have nothing to do with me. I hasten to add he committed adultery and left us!
My advice is to stand your ground and take control. It's tough but as the primary carer you deserve some respect in all matters to do with your children. Mine are teenagers so I leave it to them now to maintain relationships with their father and his mother.
Hope this helps and good luck xx